Automatic focusing optical-projection apparatus



July 17, 1928. 1,677,778

E. K. HUNTER AUTOMATIC FOCUSING OPT ICAL PROJECTION APPARATUS OriginalFiled Sept. 20. 1922 Patented July 17, 1928.

UNITED STATES PATENT} OFFICE.

EDGAR KENNETH HUNTER, 01 LONDON, ENGLAND, ASSIGNOR TO JOHANNES ROBERTCARL AUGUST, OF LONDON, ENGLAND.

AUTOMATIC FOCUSING OPTICAL-PROJECTION APPARATUS.

Original application filed September 20, 1922, Serial No. 589,365, andin Great Britain September 21, 1821.

Divided and this application filed De The present invention relates toapparatus for enlarging or otherwise copying in which the focus ismaintained automatically while adjusting for various scales of enlarge-5 ment or reduction and is a division of my co-pending applicationSerial No. 589,365,

filed Sept. 20, 1922.

The object of the present invention is to provide a simplifiedconstruction of appam ratus embodying such cam controlled mechanism andwhich will automatically b adjustment of a single member either en argean image or reduce it as desired.

In apparatus according to the present invention the lens is positivelyactuated, for example, by a screw shaft, and 1s connected to the othermovable element by levers pivoted together and pivoted to the lens andto the other movable element, the levers being controlled by one camsurface for the enlarging range and by a second cam surface for therange for reduction. The pair of pivoted levers and the cams may be du-26 plicated.

The invention is more particularly de-' scribed with reference to theaccompanying drawings in which Figure 1 is a diagrammatic plan view ofan arrangement according to the present in- 3 vention.

Figure 2 is a corresponding view of the linkage and its controllingmechanism.

Figure 3 is a detail.

In the arrangement shown in reference 35 to Figure 1 the receptivesurface may comprise a plate such as 1 inserted within a fixed holder 2whilst a lens element 3 in a carrier 4 is displaced along its opticalaxis by means of a nut upon it engaging with a threaded spindle 5operated by means of a hand-crank-fi. A frame 7 is provided to re- Jceive a slide 8 or other translucent obje to be illuminated by a sourceof light This carrier 7 for the object 8 is connected to the lenselement 3 by means of bellows 10 of usual construction and is guidedalong the optical axis.

Two pairs of hinged levers 13, 14 forming a lazy-tongs are connected tobracket extensions of the lens carrier-4 and frame 7 by pivots 11, 12respectively whose axes intersect the optical axis: thus the pivots areconstantly guided along a line parallel to cember 18', 1925. Serial No.78,288.

the optical axis. The outer pivots 15 of the llnks have rollers 16 heldin engagement with cams 17, for example, by means of a welght or spring.Thus as the lens element 3 is progressively moved towards" the fixedreceptive surface 1 by means "of the hand crank 6 so will the object 8follow the lens element 3 along the optical axis at a slightly lesserrate of displacement until the ob- ]ect has reached a position such asthat indicated in dotted lines, which will correspond to the position ofequal or unitary size of image projection in which the lens element 3will then lie at the principal focus point between. the slide 1 and theobject 8.

Further progression of the lens element 3 towards the receptive surface1 by a continued operation of the hand-crank 6 then brings the sides ofthe toggle links 14 into engagement with the cams 18 which for allfurther forward movement of the lens control the toggle links so thatthe object 8 moves in the reverse direction. to the movement of thelens. It follows that the rollers. 16 will be constrained to leave thecams 17 which are inoperative, only one set of cams,

either 17 or 18 being operative at one time.

Due to the progressive forward movement of the ivot 11 along the opticalagzis the front sides of the links 14 are pushed against the cams 18 andslide on these as the pivots 15 are drawn inwards towards one another.

The cams 17, 18 will be plotted in such manner that the linkage 13, 14maintains the Newtonian law of distances between the reoeptive surface 1and the lens 3 and the distance of-this lens 3 from the object 8.

It will be desirable to provide means for indicating the particular sizeof magnification or reduction of, the image. This may be done by a scaleattached-"to any-.of the movi members or as shown in Figures 2 and byplacing a graduated disc 46 on a spindle 50 mounted in bearings (notshown) to lie arallel with but below the optical axis. e spindle carriesa spiral ste drum 51 each step of which 52 oorrespon s with a particularratio of magnification or reduc-- tion of the image. With suchconstruction, as the pivot 11 of the linkage is fed forward by thethreaded spindle 5, a pawl finger 53 on the pivot 11 will be movedforward with it until it will come against the desired said step 52 onthe shaft 50, whereupon the further displacement of the lens-andconsequent displacement of the object will be arrested.

It will be seen that by the above means it will be possible to veryaccurately and rapidly set the parts for any desired ratio ofmagnification or reduction and this setting can be repeated whendesired.

I declare that what I claim is 1. An optical projection systemcomprising an object holder, an image holder, a lens holder, movablemounts for two of said holders, a cam controlling the displacement ofone holder in a forwardly progressive direction, a second camcontrolling the movement of the other holder, first in a forwardlyprogressive direction and then in a reverse direction, and means toprovide relative displacement between said holders and said cams whilstmaintaining the relationship of the three holders according to theNewtonian law of conjugate foci.

2. An optical projection system comprisin an object holder, an imageholder, a lens ho der, movable mounts for two of said holders, a camcontrolling the displacement of one holder in a forwardly progressivedirectlon, a second cam controlhng the movement.

of the other holder, first in a forwardly progressive direction and thenin a reverse direction, and means to provide relative displace mentbetween said holders and said cams whilst maintaining the relationshipof the three holders according to the Newtonian law of conjugate foci, adrum controlling said relative motion between said cam surfaces and saidholders, and means to angularly rotate said drum so that equal angulardisplacements of the drum correspond to equal linear increases in sizeof the image projected. I

3. An optical projection system comprising an image holder, an objectholder, a lens, a toggl linkage between said lens and said objectholder, means to progressively displace the lens along the optical axis,a set of cams controlling the floating pivot of said toggle linkageduring said progressive displacement, means to further progressivelydisplace the lens along the optical, axis, and a second set of camscontrolling the side of one link of said toggle linkage during saidfurther progressive displacement.

In witness whereof, I have hereunto signed my name this 4th da ofDecember, 1925. EDGAR KE N ETH HUNTER.

